The present invention relates generally to blue/green screens for use in chromakey applications and, more specifically, to an improved blue/green screen used in chromakey recording.
Blue and green screens are used in video and film production for chromakey application. Basically, people and objects are placed in front of a blue or green screen that reflects monochromatic light. The camera picks up this monochromatic light and image-processing equipment (that is, hardware and software) then substitutes different images where the blue or green color (i.e., the chromakey) appears.
In this way, people and objects can be placed in virtual settings in the resulting video.
Another application is that foreground objects may also reflect the same color and hence be chromakeyed. This is difficult as it is very hard to get the object illuminated in an even enough manner to chromakey.
Another chromakey device is a product called Chromatte™ fabric, formerly HoloSet. Chromatte is a highly reflected fabric having glass beads therein that is used in conjunction with a circle of monochromatic lights around the camera lens of pure blue or green light to give the blue or green screen effect. There is a practical problem using Chromatte fabric with cameras having teleprompters mounted thereon because of the bright lights.
Another method for chromakey production describes the use of phosphorescent material, as shown in U.S. Pat. No. 4,417,791 to Erland et al. A red phosphorescent material is used as a chromakey, which is exposed to visible light, while blue and green phosphorescent material are used as chromakeys and are activated by being exposed to ultraviolet radiation or light. Phosphorescent material is exposed to the light source during the different recording or photographic steps. Filters are required to eliminate and distinguish between the illuminating source and the illumination produced by the chromakey. The use of multiple light sources limits the applications in which this chromakey system may be used. It requires additional sources of light, which may not be available or undesirable to be activated during the recording of a scene.
In an attempt to address some of these problems, Erland in U.S. Pat. No. 5,972,440 uses daylight/fluorescent as a chromakey matte. Though eliminating the requirement for a special lighting, fluorescents require continuous exposure to a source of light in order to radiate light. Thus, the daylight/fluorescent is not desirable in low light situations.
An early use of fluorescent material and phosphorescent material to create special effects in films is described in U.S. Pat. No. 3,085,877. By using visible light, ultraviolet light or infrared radiation, the whole scene or selective portions of the scene coated with the luminescent category of materials were illuminated. A method of double exposure and a method of selectively turning the illumination source on and off are described to create the desired effect. The after glow effect of phosphorescent material is recognized but not used in a color key system.
The present invention is a method of chromakey recording, which includes providing, in a scene, a chromakey material which is capable of continued luminance without activating light. The chromakey material is activated and the scene is recorded without activating light while the chromakey material is luminescing. The chromakey material may be an electroluminescent material that is activated by applying electrical energy to the chromakey material. The chromakey material may also be a phosphorescent material, which is activated by applying light to the phosphorescent material. The light is removed from the phosphorescent material during recording.
These and other aspects of the present invention will become apparent from the following detailed description of the invention, when considered in conjunction with accompanying drawings.